Thank you for your post.
Is it any 2nd database, or is it a particular database file? Are there any other users accessing hosted files? Are any files set up for ODBC? Instant Web Publishing? Custom Web Publishing? Does the Event.log file provide any clues?
Try uninstalling and reinstalling FileMaker Server 11. Deploy the server and make sure everything is running correctly. Access the hosted files again.
Any other information you can provide may be helpful.